Ok, so after reading it (and with some background in Biochemistry :) ) : DNA can form structures other than just the classical 'helix' shape. For example a ht

Ok, so after reading it (and with some background in Biochemistry :) ) : DNA can form structures other than just the classical 'helix' shape. For example a https://en.wikipedia.org/wiki/G-quadruplex https://en.wikipedia.org/wiki/G-quadruplex which form at the end of the helix. This paper shows that deleting one 'TET' gene (https://en.wikipedia.org/wiki/TET_enzymes https://en.wikipedia.org/wiki/TET_enzymes) leads to an increase in certain types of cancer. The protein encoded by that gene removes methyl (-CH3) groups from DNA, in a process called demethylation. The 'opposite' process of methylation, in this case, is performed by the enzyme DNMT1 - and if you delete both TET and DNMT1 genes, there are less of these non-helical DNA structures and less cancer. So the conclusion is that an imbalance between metylation and demethylation of the DNA can lead to cancer.